The invention relates to a ternary intermetallic-compound capable of reversibly sorbing hydrogen. More specifically, this invention relates to a ternary intermetallic-compound capable of gettering hydrogen at low pressures and at temperatures from about room to about 200.degree. C. and which can be regenerated at low pressures and at temperatures from about 300.degree.-500.degree. C. The temperature and pressure ranges at which gettering and regeneration can occur can be controlled by varying the composition of the compound.
It is generally recognized that impurities in the plasma of magnetic confinement fusion devices such as Tokamaks can seriously limit the performance of such devices by lowering the plasma temperature and quenching the fusion reaction. These impurities are introduced into the plasma by a variety of sputtering and erosion processes occuring at the walls of the devices by hydrogen isotope recycling. These impurities may consist of oxygen, carbon and hydrogen, including the isotopes deuterium and tritium Some metal ions may also be included which have been sputtered from the wall of the device during operation.
Some solutions to the problem of impurity control include modifying the recycling processes, minimizing the erosion rates at the surfaces facing the plasma and removing the offending impurities from the plasma. It has been shown that the trapping and subsequent re-admission of hydrogen isotopes from walls affects plasma profiles, especially at the edge, substantially modifying impurity influxes. In deuterium-tritium burning devices, wall recycling will strongly influence tritium inventory, which must be held to within well-defined limits. Therefore, tritium retention is an important factor in the design of a suitable fusion device.
There is need for a material which can getter hydrogen and hydrogen isotopes under the low pressure, high temperature conditions present in operating magnetic containment fusion devices. Furthermore, the material must be capable of being regenerated for recycling under reasonable condition of pressure and temperature. Such a material can be placed in the fusion device either as a coating on the walls of the device or as a coating on sheets of substrate which can be placed within the device. Preferably the material is reasonably selective for hydrogen, must be able to function as a hydrogen and hydrogen isotope getter at pressures down to at least 10.sup.-6 torr, in the presence of power fluxes up to about 50 w/cm.sup.2 and at temperatures from about room temperature up to about 200.degree. C. Furthermore, the material should have a high hydrogen capacity in order to reduce the frequency of regeneration, it should be able to be regenerated with respect to absorbed hydrogen at a relatively low temperature, preferably no higher than 500.degree. C., and it must be able to function as a hydrogen getter in the presence of other contaminant gases, such as CO, O.sub.2 and N.sub.2.
One such material which has been used successfully is sublimed titanium. However, titanium is not easily regenerated and fresh layers of titanium must be sublimed for each gettering cycle that is required, which is expensive and time consuming. Another material which fulfills many of the requirements is ST101.RTM.. This material is a proprietary Zr-Al based alloy available from SAES Getters of Milan, Italy. However, hydrogen capacity of the alloy is somewhat limited and regeneration of the alloy within a reasonable length of time requires that it be heated to temperatures of at least 750.degree. C.